Enantioselective synthesis of 2-allyl and 2-(3-trimethylsilylpropargyl)-2-hydroxycyclohexanone using osmium-catalyzed asymmetric dihydroxylation
摘要:
The catalytic asymmetric dihydroxylation of (1-cyclohexenyl) or (1-cyclopentenyl) acetonitrile 5 and 15 with AD-mix-beta occurred with good enantiofacial selectivity (87 to 94.7% ee after recrystallization) giving (R,R)-diols in agreement with the mnemonic device. The 6-membered ring diol nitrile was easily transformed, via standard functional group manipulations, to 2-allyl and 2-(3-trimethylsilylprop-2-ynyl)-2-hydroxycyclohexanone in about 35% overall yield. (C) 1998 Elsevier Science Ltd. All rights reserved.
pargyl)-2-hydroxycyclohexanone were respectively obtained by resolution from the corresponding diastereomeric acetal derived from C2-symmetrical diol or from the camphanate ester. Study of the rearrangement of their corresponding imine derivatives has shown that it occurred with complete retention of the stereogenicity.